@Maaz..
Xulfi Bhai Means A Bleed Nut Welded On Your Custom Built Water Pipes In Order To Bleed Air Trapped Inside System Due To Relocation Of Pipes.....!!! You Have To Pass Water From The Place In Order To Make Sure There's No Air Left Inside Blocking Ways And Causing Coolant Surge And Heatups
Its Mostly A 12mm Or 14mm Nut.....!!! It Helps Me Alot In My NISSAN GA15DS.....!!
Here 90% Mechanics Die Trying And Later Blame NISSAN For Their Faulty GA Series Motors And Crack Heads......!!!
They DOn't Even Bother To Know That There's A GODDAMN Air Bleed Nut Given There For A Purpose....!!!
It Happens with Me As When We Start Our Motor GA15DS...Mechanic Complains About High Buildup Head Pressure And Engine Heatups.....!!
Next Day I Bleed It And It Gets Cool Like Anything..............!!!